5.56 Ammo Help

I'm looking at buying either a case of IMI M855 from wideners or the Lithuanian (GGG) ammo from ammoman. I hear good reviews regarding the IMI but can't seem to find much about the GGG 5.56. Anyone have any input on these two and which do you feel is better quality. Shooting this out of an Armalite M15A4 and RRA mid-length. 1:9 twist.